1. Field of the Invention
The present invention relates to a glass used as a sintering aid for a resorbable moulded body containing calcium phosphate as well as to a method for manufacturing said moulded body.
2. Description of the Related Art
Inorganic bone replacement materials can be divided into resorbable and long-term stable materials. They are selected and used according to the specific medical indication. Materials based on tricalcium phosphates are state of the art as regards the use of resorbable products contributing to a direct contact of bones. In most cases, granulated materials having different grain sizes are used. There is the problem, however, that during biodegradation and the simultaneous growth of new bone tissue, the granules remaining in the bone defect which has been operated and filled with the granulated material are pressed against one another and prevent a complete dissolution of the bone replacement material. The aforesaid problem can be solved in different ways. One method consists in developing materials which can be resorbed more rapidly (e.g. EP 541564 B1), another one consists in providing the granulated materials with an inner porosity thus facilitating their dissolution once they have been pressed against one another (e.g. DE 19744809 C1).
In principle, the problem can also be solved by manufacturing an open-pore and at the same time large-pore moulded body. This can be done by pressing or isostatically pressing the starting material, subsequently sintering it and finally providing it with the pore structure by boring, etc. using various techniques (mechanically, using dry ice, etc.), by means of so-called free-form fabrication techniques or according to the known sponge impregnation technique with subsequent sintering (Schwartzwalder-Somers process).
The aforesaid solutions frequently have the disadvantage that the tricalcium phosphate to be used is not sintered to a sufficient degree and, as a result, the moulded bodies obtained are relatively unstable from a mechanical point of view.